Pyrethroid insecticides exposure increasing in homes and people

Exposure to pyrethroids is increasing, with the insecticides found in two-thirds of adults, children, and homes tested, according to a new study led by University of California, Davis researchers.

In addition, children are still widely exposed to chlorpyrifos, an insecticide that was banned for household use over a decade ago. [Chlorpyrifos received the same household ban in Canada at about the same time but is still licensed for some uses.-GS]

The pesticides were measured in the urine of children and adults in 90 northern California families, and in floor-wipe samples taken inside their homes. The results provide the first evidence that indoor use of pyrethroids is an important contributor to children’s exposures.

Pyrethroids found in mums

Pyrethroids, which are manmade versions of compounds found in chrysanthemum flowers, are used in a variety of household sprays, aerosol bombs, insect repellents, pet shampoos, and lice treatments. At high doses, they can cause neurological effects, such as dizziness and nausea. The potential health effects from chronic, low-level exposure are largely unknown.

Use of pyrethroids has grown in the United States as they have replaced chlorpyrifos in many household products.

The northern Californians tested in 2007-2009 had average urinary concentrations of a pyrethroid breakdown product that were more than twice as high as levels reported for a national study in 2001-2002. The chemical was detected in more than 60 percent of people studied.

“Measurements from the 90 northern California households highlighted in this paper show pyrethroid exposure occurs commonly, based on the frequent detection of several pyrethroid metabolites in participants’ urine and frequent detection of both insecticides and their metabolites in the floor-wipe samples,” the authors wrote in the journal Environmental Science & Technology.

At the same time, levels of a breakdown product of chlorpyrifos were on average 21-percent lower in the children who participated in the new study than in the nationwide study six years earlier.

Almost all floor samples tested positive

Nevertheless, 99 percent of the floor wipes and 65 percent of study participants still had traces of chlorpyrifos. The chemical was banned for household use in 2001 because of risks to children’s developing brains, but the Environmental Protection Agency still allows its use on crops.

The scientists said children may be less exposed to chlorpyrifos because of reduced use in agriculture as well as the ban of products inside homes. However, organophosphates such as chlorpyrifos are “still present in agriculture, thus exposure to these insecticides through the food pathway continues”, they wrote.

In children, but not adults, higher concentrations of pyrethroids found in floor wipes were associated with higher urine levels. This suggests that children may be receiving a higher portion of their exposure from inside the home. Children often play on the floor and put their hands in their mouths, so they may be more exposed from house dust.

“To our knowledge this is the first study evaluating correlations between floor-wipe and urinary metabolite levels for pyrethroids, and it demonstrates the usefulness of floor-wipe samples as indicators of pyrethroid exposure for children. The resulting correlation provides evidence that children are being exposed to pyrethroid insecticides in their home, and thus indoor use is an important contributor to exposure,” the authors wrote.

Further research needed for long-term effects on kids

The scientists added that “further research is warranted to…understand whether these compounds have long-term effects on child health or development.”

A small study of children in China linked residential pyrethroid exposure to childhood leukemia in 2012. Other studies in Japan and China linked it to changes in men’s sperm. Some research indicates that pyrethroids may be endocrine disruptors that mimic or block estrogen.